The invention relates to a method of making a solid-liquid filtration cloth, the method comprising: weaving a solid-liquid filtration cloth comprising a first surface and a second surface; employing a plurality of longitudinal polymer yarns and a plurality of cross-direction polymer yarns in the weaving; and providing the solid-liquid filtration cloth with a permeability allowing liquid in a mixture to be solid-liquid filtered to permeate the cloth and, on the other hand, preventing solids from the mixture from passing the cloth.
The invention further relates to a solid-liquid filtration cloth comprising: a first surface and a second surface; a plurality of longitudinal polymer yarns and a plurality of cross-direction polymer yarns; and the solid-liquid filtration cloth having a permeability allowing liquid in a mixture to be solid-liquid filtered to permeate the cloth and, on the other hand, preventing solids from the mixture from passing the cloth.
The invention still further relates to a solid-liquid filtering device comprising: at least one filter surface having a plurality of openings; means for moving the filter surface in a rotational direction during the filtration; and a solid-liquid filtration cloth arranged against each filter surface, the solid-liquid filtration cloth having a permeability arranged to let through liquid in a mixture to be solid-liquid filtered and, on the other hand, arranged to prevent solids from the mixture from passing the cloth.
For example in the mining industry, in the refinement of metals, the forest industry, the chemical industry, and manufacturing processes for foodstuffs and pharmaceuticals, there is a need for solid-liquid filtration for separating liquid and solid particles from a mixture of solids and liquid. Various mechanical filtration apparatuses with different operating principles and properties have been developed for solid-liquid filtration. Known apparatuses include vertically and horizontally arranged chamber filters, belt filters, double fabric presses, horizontal filters, and disc and drum filters. In all these apparatuses, the principle of the filtration is to separate the liquid phase and the solid phase at least partly from each other by means of a pressure difference. Furthermore, in mechanical solid-liquid filters, the filter surface of the filtration apparatus is provided with a filtration cloth, which operates as a filtering layer. In some filtration apparatuses, the filtration cloth is moved during filtration, controlled by suitable rollers either continuously or in cycles. Furthermore, for example in disc and drum filters, a filter surface provided with a filtration cloth is moved in a basin containing a mixture to be processed, so that solids are caught on the surface of the cloth. The filter surface is moved with respect to doctor blades or the like, which guide the solids accumulated on the outer surface of the filtration cloth away from the cloth.
A factor influencing the capacity of a solid-liquid filter is the size of the filtering area of the filter. For example, in a disc or drum filter, the filtering area can be increased by increasing the diameter. However, the problem herein is that the size of the filter and, at the same time, its space requirement increases disadvantageously, whereby the efficiency of the production space per floor area may be reduced. Drum filters having corrugated sector element sides, i.e. filter surfaces, have been developed for solving the problem. A corrugated filter surface allows a larger filtering area to be provided in a disc filter than previously. In this way, the filtration capacity of a disc filter is increased without any significant change in the outer dimensions of the filter. However, the problem in this solution is the requirement that the filter sector of a disc filter be replaced with sectors provided with a corrugated filter surface. Replacement of the sectors causes significant extra costs. In addition, costs and problems arise because changes in the sectors usually cause changes also in other components and control parameters of the filtration apparatus. Accordingly, the problem is how to increase the capacity of existing filtration apparatuses.